Substitute for calgon in C-22 process?

Hi friends, I've been looking into C-22 processing using the recipe from Patrick Dignan's Simplified Color Processing Formulas. The recipe calls for calgon which has proven to be a bit confusing. A post a few years ago says that the recipe for calgon changed 20-30 years ago and that it should be substituted with either sodium hexametaphosphate or Disodium EDTA. Anyone know which one of these is best for C-22 process?

Thanks!

A process that old would probably use sodium hexametaphosphate, but it's certainly optional and you can simply use deionised water.

I see, thank you so much!